Holland-Bill L, Christiansen CF, Ulrichsen SP, et al. Validity of the International Classification of Diseases, 10th revision discharge diagnosis codes for hyponatraemia in the Danish National Registry of Patients. BMJ Open 2014;4:e004956. During the production process an error was introduced in table 2 of this paper. In the last column ‘Validity measures, % (95% CI)’ the first ‘Sensitivity’ value listed in row 1 should be ‘1.8 (1.7 to 1.8)’ (and not ‘8 (1.7 to 1.8)’).